/Engine/Plugins/Runtime/MassEntity/Source/MassEntity/Public/MassEntityQuery.h
A query to be considered valid needs declared at least oneEMassFragmentPresence::All,EMassFragmentPresence::AnyEMassFragmentPresence::Optionalfragment requirement.
[USTRUCT](Programming/UnrealArchitecture/Reference/Structs)() struct FMassEntityQuery : public [FMassFragmentRequirements](API\Plugins\MassEntity\FMassFragmentRequirements), public [FMassSubsystemRequirements](API\Plugins\MassEntity\FMassSubsystemRequirements)